Measuring and control apparatus



Oct. 25, 1949. MACHLET Re. 23,160

MEASURING AND CONTROL APPARATUS Filed Nov. 25, 1941 3 Sheets-Sheet 1 Oct. 25, 1949. G. A. F. MACHLET Re. 23,160

MEASURING AND CONTROL APPARATUS Filed Nov. 25, 1941 v 4 s Sheets-Sheet 2 Oct. 25, 1949. ca. A. F. MACHLET Re. 23,

MEASURING AND CONTROL APPARATUS Filed Nov. 25, 1941 3 Sheets-Sheet 5 Reissu ed on. 25, 1949 UNITED STATES PATENT OFFICE MEASURING AND CONTROL APPARATUS George A. F. Machlet, Elizabeth, N. J.

Original No. 2,414,314, dated January 14, 1947,

46 Claims.

This invention relates to measuring and control apparatus, and more particularly to apparatus of high sensitivity that responds to variations in one or more factors, such as temperature, pressure, direction, current flow or the like, to record the changes in value and/or to energize a control system in accordance with the change in a control function or the integrated changes in a plurality of control factors.

For simplicity of explanation, the invention will be described with reference to control systems for regulating the supply of a fluid fuel to a burner to maintain a desired temperature within an oven or treating chamber, which temperature may be constant of varied by a progressive control system, but it is to be understood that the control action may be based upon some function or quality other than temperature and that the controlled element may be a recording stylus or a modulating device other than a fuel supply valve.

Electronic recording and control systems have been employed to obtain a proportionate response or a corrective influence from highly sensitive measuring instruments that do not develop sufficient force to effect a mechanical closure of relay contacts; and some of the prior systems, for example those disclosed in my prior Patent 2,056,285 and Reissue Patent 21,345, establish a corrective influence that varies in magnitude with the departure of a measured function from a preselected standard value. Such proportioning control systems provide a continuous re-establishment of equilibrium in the controlled process or apparatus by varying the corrective influence in accordance with changes in the supply and/or demand conditions. The control action is based upon the existence of a measurable departure of the magnitude of the controlling function from a preselected value; and the rebalance for establishing an equilibrium between demand and supply factors, upon variation in the magnitude of either or both, has not been effected at the one preselected value of the controlling function but over a value range determined by the sensitivity of the control apparatus and by the time delay between a change in operating conditions and the detection of a measurable variation in the magnitude of the controlling function.

The stabilization of the conditions affecting the process was thus'obtained by a rebalance of the control system at an operating point other than the desired preselected value of the controlling function in the prior proportioning control systems of the electronic type. -The present inventlon contemplates a rebalance of the control system at the preselected operating point, i. e. at the desired value of the control function, upon any variation of the process conditions that effects a departure of the measured function from a preselected value. The rebalance of the control system for operation about a single control point will be designated hereinafter as a resettingfof the control system, thereby to distinguish from the rebelancing of the operating conditions affecting the process. The operations for rebalancing the process conditions and forresetting the control system take place at the same time but the resetting of the control system must proceed more slowly than the rebalancing of the conditions affecting the process to avoid conflict between these operations and to insure a final equilibrium.

Objects of the present invention are to provide electronic measuring and/or control systems of simple and efilcient design that effect a rebalance of conditions affecting the controlled process or apparatus by a complementary rebalance of the control system. An object is to provide measuring and/or control systems of high sensitivity that include devices for effecting an initial and rapid rebalance of the operating conditions affecting a controlled process or apparatus upon the de parture of a controlling function from a preselected value, and for effecting a subsequent resetting of the measuring and/or control system for operation at the preselected value. Other objects are to provide simple and effective control systems for regulating the heat supplied to an oven, retort or the like in accordance with the temperatures at the exterior of and within the heated device, thereby to reduce the temperature fluctuations within a device across which there is a substantial temperature drop.

These and other objects and advantages of the invention will be apparent from the following specification when taken with the accompanying drawings in which:

Fig. 1 is a circuit diagram of an embodiment of the invention as applied to the regulation of the fuel supply to a heating furnace;

Fig. 2 is a fragmentary circuit diagram of an embodiment including elements for resetting the control system to operate about a preselected control point;

Fig. 3 is a fragmentary circuit diagram of another embodiment in which the resetting devices include adjustable reactors;

Fig. 4 is a central vertical section through the oscillator coils and. associated elements of the Fig. 3 circuit;

Fig. 5 is a circuit diagram of a control system,

including two associated control circuits, for regulating the heat input to an oven or retort in response to temperature changes within and at the exterior of the oven or retort; and

Fig. 6 is a circuit diagram of another embodiment of a temperature control system of the dual control type of Fig. 5.

In the drawings, the reference character I identifies a sensitive measuring instrument having a, movable system that is displaced angularly in accordance with the voltage developed by a thermocouple T, the pointer of the moving system carrying a small vane I that affects, in accordance with its displacement, the oscillatory conditions in an oscillatory circuit comprising the coupled inductances LI, L2 and a tuning condenser 2. The moving vane I may alter the capacity across one or both of the inductances, the coupling between the inductances or, as illustrated in Fig. 1, the eil'ective value of a split inductance 3 that is a part of the inductance Ll.

The high potential terminal of the oscillatory circuit is connected through a coupling condenser l to the control grid GI of an oscillator tube 5 in conventional manner. The oscillator tube elements, as illustrated, include a screen grid G2 connected to the anode A through a radio frequency choke 6 and to the cathode K through condenser I, and a suppressor grid G3 that is connected to the cathode K within the tube. The junction of the inductances LI, L2 is connected to the cathode K, the outer terminal of L2 is grounded, and the control grid is returned to ground through the usual bias resistor R.

The oscillatory current developed in the oscillatory circuit is impressed upon a'rectifier by a lead 8 that extends to the joined grid electrode G and plate A that cooperate with a second cathode K within the tube 5. Separate oscillator and rectifier tubes may of course be substituted for the dual purpose tube 5 shown in Fig. 1. The rectifier cathode K is connected through a filter network'il to the control grid G of the amplifier elements of a second dual purpose tube II. The screen grid GI is connected directly to the positive terminal +B of a direct current source that may be a voltage divider resistor II. The suppressor grid G2 is connected to the cathode K of the amplifier, and the anode A is connected to the +28 terminal through a sensitive relay that may be of the polarized type or, as shown, an instrument relay having a moving system including the pivoted coil I2 and contact arm I3. The

. voltage divider I I is energized through the rectifier section of tube III, which rectifier comprises a cathode K connected to the +3 terminal and an A negative bias is impressed upon the grid GI of tube In by connecting the grid through a high resistance It to a more negative point on the voltage divider I I than that to which the cathode K is connected by a lead II. The negative bias is 01 such magnitude that the amplifier is biased to- 4 I the relay is so adjusted or designed that the movable contact I3 hovers between the opposed stationary contacts lta, lib at a definite predetermined plate current value. i

The relay contact arm I3 is connected to the power supply lead L, and the contacts I3a. I3b are connected to the outer terminals of 'the split field windings of a reversible motor M that actuates a recording stylu or, as shown, a cam I5 or other means for adjusting the modulating valve IS in the fuel supply system to a furnace or heater. The apparatus for rebalancing the system upon a change in operating conditions l1 along the resistor I8 that is connected between coil L3 and the +B terminal of the direct current source II. The other side of the coil L3 is connected by lead III to a tap II that is adjustable along the voltage divider II. The coils L2 and L3 are coupled magnetically by the saturating core I9.

Assuming that the oven or furnace temperature is at its normal desired value, the measuring instrument I locates the vane I in such position, with respect to the split inductance 3, that the rectified current output of the oscillator-rectifier tube 5 is at the preselected value for which the current output of the tube It holds the relay contact arm I3 in open circuit position in the narrow gap between the contacts I311, lib. A

change'in the temperature at the thermocouple T will alter the voltage input to the sensitive measuring instrument I and thus displace the vane I with respect to the split inductance 3. The oscillator balance is thus disturbed and the current fiow thereby altered, and in turn the plate current of the amplifier tube III is altered and the relay contacts close to energize the motor M for operation to adjust the fuel supply valve IS in the proper sense. Assuming that the vane movement is such that the tendency towards oscillation is reduced, the motor M rotates clockwise until a rebalance is eiiected by the increased flow of current to coil L3 of the saturating core reactor. The increased current input to coil L3, due to the reduction in the eiIective value of the resistor I8, increases the tendency towards oscillation and the rectified current output of the oscillator-rectifier tube 5 thu increases until the plate current output of the amplifier III shifts the range of the control relay to a negligible value.

The system can be reset for operation at the desired control point by introducing a delayed corrective action through electrically heated elements that affect the oscillatory circuit.

The resetting control system of Fig. 2 includes all elements of the Fig. 1 circuit except that the instrument controlled variable element takes the form of a condenser blade I that moves with respect to a stationary condenser plate 3 that is connected to the high potential and oi the oscillator inductances Ll, L2. For greater clarity of illustration of the resetting circuit elements, the oscillator and amplifier section of the system that lies within the broken line rectangle A of Fig.

1 is indicated by the block element OA in-Fig. 2. The rebalance of operating conditions is effected, as described above, by the motor-produced adjustment of the resistor arm ll to alter the current flow to the coil L3 of the saturating core reactor.

The resetting system comprises temperaturevariant condensers 22, 23 shunted across the instrument condenser I-3' and the coupling condenser respectively, and the associated heater resistances 24, 25 that have a common grounded terminal and receive currents that are varied in magnitude, and in opposite sense, by the motor M. The current supply to the heater resistances is from the power lead L, through the adjustable series resistor 26 to the common terminal of the resistors 21, 28 whose outer terminals are connected to the heater resistors 24, 25, respectively, through the contacts of the undercurrent relay 29u and the overcurrent relay 290 that are serially arranged in the plate circuit of the output tube Ill. The effective values of the resistors 21, 28 are adjusted in opposite sense, upon rotation of the motor M, by contact arms 30, 3|, respectively, that are carried by the motor shaft and connected to the outer terminals of the resistors. The switch systems of the relays 2911., 290 are of the double pole, double throw. type and comprise serially arranged polarity reversing switchesbetween the adjustable resistors 21, 28' and the heating resistors 24, 25 of the temperature-variant capacitors 22, 23, respectively. Under normal operating conditions, the plate current of tube I0 is suflicient to energize the undercurrent relay 2111. to attract the armature but is below the value that will lift the armature of the overcurrentrelay 290. When the measured temperature departs substantially from the normal confor modulated control of the heat input, and

the undercurrent relay 2911. drops to open position or the overcurrent relay 290 closes. Each of these perature is below the effective same 22, 23 takes place at a relatively slow rate and gives rise to a further unbalance of the oscillatory system, resulting from and approximately equal to the initial unbalance due to instrumentproduced movement of the vane I, that produces another energization of the motor M to effect a further adjustment, and in the same sense, of the fuel supply valve IS. The fuel supply is thereby adjusted beyond the point that establishes a rebalance of the operating conditions at a new temperature, and this exaggerated change in the fuel supply results in a shift of the furnace temperature back to its initial preselected value.

The undercurrent relay 29a reverses the resetting circuit connections when the measured temcontrol range of the apparatus. This condition will arise when a furnace is started. cold or when the control point is adjusted to a new temperature value during the heating process. If the resetting system remains operative during a relatively long heating-up period, the temperature-variant condensers 23, 22 will accentuate the unbalance of the oscillatory circuit and thereby delay the initial closing adjustment of the fuel valve l6 until the furnace temperature reaches a value substantially above the lower limit of the normal control range. The resetting system would thus function to shift the desired control point to a higher value, and a number of over-adjustments of the fuel valve would be effected before stable operating conditions were established. The resetting operations will reverse the connections between V the outer terminals of the control resistors 21, 28 and the heating resistors 24, 25. For all conditions of the polarity reversing relays 2911 290, the angular movement of the motor shaft adjusts the effective values of the resistors 21, 28 in opposite sense, and thereby alters the current flow in the heater resistors 24, 25 in opposite sense to effect corresponding changes in the effective values of the condensers 22, 23.

Assuming, as in the above discussion of the Fig. 1 circuit that the operating conditions alter from normal in such sense that the instrument I moves the vane l to reduce the tendency towards oscillation, the relay coil l2 closes the contacts to energize the motor M to adjust the fuel supply valve I6. The rebalance of operating condition is effected at once by the adjustment of the value above about 15 milliamperes.

system is therefore rendered inoperative or, as illustrated, is preferably reversed in its sense of operation to accelerate a modulating control action as the measured temperature approaches the normal control range. The overcurrent relay 290 is similarly operative to reverse the sense of operation of the resetting system when the measured temperature is substantially above the normal control range. This condition may arise in the operation of a program control system when the temperature control point is suddenly shifted to a lower value.

The plate current of tube Ill may vary from about 6 to 15 milliamperes to adjust the modulating fuel valves I6 from its closed to open position, and the relays 25m and 290 are then adjusted for a. drop out of relay 2% when the plate current drops below 6 milliamperes and an energize.- tion of relay 290 when the plate current rises One of the polarity reversing relays may be omitted when the particular heating process is of such nature that the measured temperature can depart in only one sense from the normal control range. The reversal of the resetting action is usually desirable to accelerate the control action when the measured temperature is outside of the normal control range for a substantial time interval. It is practical in some installations, however, to obtain a satisfactory control" of temperature by rendering the resetting system inoperative when the meassystem 0A similar to or identical with that shown in Fig. 1. The initial unbalance of the oscillatory circuit may be effected by the inductance varying system of Fig. 1 or, as illustrated, by a small inviously described. The power supply to leads L,

L' for energizing the system must be from an alternating current source AC in this form of the invention.

The oscillatory circuit inductances Li, L! are of conventional design, and the rebalancing coil L4 has a loose magnetic coupling to the oscillator coil L2. The coil L4 is connected to an inductance 32 that is varied in magnitude by a core 33, of magnetic or non-magnetic material, on a lever or walking beam 34 that is adjusted angularly by a crank arm 35 on the shaft of the motor M.

Current flow in the-oscillatory circuit is aflected by the impedance of the coupled circuit that includes the coil L4 and the inductance 3!, and this impedance is altered,by movement of the core 33 in such sense that an initial rebalance oi the operating conditions is effected when the motor M is energized as the result of a displacement of the instrument-carried vane l with respect to the condenser plate 3'.

The resetting of the system to the original control point is effected by varying the effective values of the inductances 31, 31 that are coupled to the oscillator coils Ll, L2, respectively. ,The in-. ductances 31, 31' comprise a few turns of wire wound upon the associated coils, see Fig. 4, and in closed series circuits with temperature-variant resistances 38, 38', respectively, of wire, preferably nickel wire, that have associated heater resistances 39, 33', respectively. The junction of the heater resistances is connected to the power supply lead L through an adjustable resistance 26, and the outer terminals of the heater resistances are connected to adjustable inductances I I 4| through the polarity reversing switch contacts of relays 29a, 230, to the power lead L, through inductances 4|, II that have associated cores 42, I2 suspended from the lever 34 at opposite sides of its pivot point. lever 34 by the motor M thus varies the effective values of the inductances l I, 4 i in opposite sense, and thereby efiects corresponding variations in the currents supplied to the heater resistances 39, 39. The relays 2911, 290 provide means for reversing or for rendering inoperative the resetting system when the measured temperature is outside of the normal temperature control range of the apparatus.

The circuit connections are such that an operation of the motor M in response to the initial unbalance of the oscillatory circuit by a measured change in the control temperature alters the heating of the resistances 38, 38' to shift the effective values of the inductances Ll, L2 to increase the unbalancing efl'ect. This increased unbalancing or resetting action is not immediately efiective but becomes apparent after the initial rebalance of the operating conditions by the variation in the value 'of the inductance 32 in series with the rebalancing coil L4.

It has been difiicult to obtain a close regulation of the temperature within ovens, crucibles and other heated units that have a relatively high temperature difierence or thermal drop across a heat-transmitting wall. An automatic control based upon the temperature within the heated unit will not respond quickly to changes in the rates of heat input and of heat demand. and a control based upon the external temperature is not possible for processes in which the heat requlrement varies during the process or in which the internal temperature is to be set at different values, either manually or automatically, during the progress of the process.

According to this invention, the automatic temperature regulator includes a primary control system that responds to the interior temperature to adjust the balance of operating point or a second control system that regulates the rate of heat input and, except as modified by the supervisory action or the primary control system, functions to maintain a constant temperature at the-exterior of the heated unit. The adjustment of the second control system may be eflected by a mechanical, a magnetic or an electrical coupling oi. the control systems.

The embodiment of the invention that is illustrated in Fig. 5 includes a mechanical coupling between a resetting control system such as shown in Fig. 3 and a control system of the type shown in Fig. 1. The equipment to which the temperature control is applied is shown diagrammatically as a crucible or pot P in a furnace chamber F that is heated by gas or liquid fuel supplied through a burner B. Thermocouples Tl; T2 are located within the pot P and in the combustion space at the exterior of the pot, respectively, and are electrically connected to the temperature measuring instruments ll, l2 that actuate small condensers Cl, C2 in the oscillatory circuits of the primary and the secondary control systems,

A tilting of the i respectively. The relatively stationaryvane of the condenser C2 of the secondary control system is carried by an arcuate rack 16 that is adjusted angularly by a worm I5 on the shaft of motor Ml of the primary control system. The primary control system of Fig. 5 is identical with that shown in Fig. 3 except for this substitution of worm i5 and rack i6 for the cam l5 and valve ii of Fig. 3. The elements of the primary control circuit are identified by the reference numerals of Fig. 3 but will not be described in detail.

The secondary control circuit is identical with that of Fig. 1 except for the substitution of the condenser C2 for the vane I .and'inductance 3 of the Fig. 1 circuit. The corresponding parts of the circuits of Figs. 1 and 5 are identified by 7 like reference numerals.

The method of operation or the temperature regulating apparatus will be described upon the assumption that the temperature within the pot P has attained the preselected control value and that both the primary and the secondary control systems are balanced, i. e. the relay circuits to the motors MI and M 01' the respective control systems are both open. Variations in'rthe fuel supply pressure or in draft conditions which cause a change in the temperature at the thermocouple T2 are compensated, as described above with reference to Fig. 1, by an unbalance of the oscillatory circuit Ll, L2, through a change in the value of the condenser C2, and this unbalance energizes the motor M to adjust the fuel supply valve It. A new balance of the operating conditions is effected 'by the adjustment of contact arm I'I along resistor l8 to alter the flow of direct current to coil L3 of the saturating core reactor. This control action takes place promptly and holds the temperature at the exterior of the pot P within close limits as the control system may be designed for high sensitivity. A change in temperature within the pot P results in a displacement or the movable vane of the condenser Cl, and thereby unbalances the oscillatory circuit and energizes the circuit of motor Ml for rotation in the appropriate sense until the operating conditions are rebalanced by the change in the value of the inductance 32 in series with the variable iron-cored inductances 4|, 4| of the re setting system, and by a displacement of the relatively stationary vane of the condenser C2 of the control system associated with the external thermocouple T2. The resetting operation takes place after a time delay, as described above, to reset the control point of the interior temperature con- ,trol system to its original value.

The motor Ml does not directly alter the fuel supply but establishes a new control point for the temperature measurements by the thermocouple T2 at the exterior of the pot P. The external control system is thereby unbalanced and to an extent substantially greater than is produced by the normal fluctuations in temperature within the combustion zone. The motor M is energized to alter the setting of the fuel supply valve IE, but the operating conditions of the external temperature control system are not immediately rebalanced by the adjustment of the contact I! along resistance II of the rebalancing circuit. Assuming that the temperature increased a few degrees within the pot P, the rebalance of the internal control system will decrease the control point of the external temperature control system by a far greater increment, for example will adjust the condenser C2 for a lowering of the external temperature by 100. change in current flow to the rebalancing coil L3 of the external control system will not rebalance the operating conditions, and a rebalance is effected only by a reduction in the external temperature, at thermocouple T2, that results in a, movement of the pointer of instrument [2 to bring the movable vane of condenser C2 into proximity to the relatively stationary vane.

A small increase in the temperature within the pot P thus results in a greatly exaggerated drop in the temperature at the exterior of the pot, and thereby quickly counteracts the rise in internal temperature. The time delay of the prior control systems is eliminated and the temperature within the heated receptacle can be maintained within close limits in spite of the thermal inertia or high temperature drop across the walls or the receptacle.

Another embodiment of a dual control system for establishing a, desired temperature within a heated receptacle is illustrated in Fig. 6. The control system that responds to variations in the internal temperature. includes a thermocouple and instrument, not shown, for adjusting the efiective value of the small condenser C I, and the network associated with the oscillator tube and amplifier tube II] is generally similar to the network illustrated in Fig. 1. The network differs from the Fig. 1 circuit in the elimination of the relay I2 as the control action results directly from variations in the plate current flow in the amplifier tube Ill. Lead 50 extends from the anode A of tube HI to the heating resistor 5| of a resetting system comprising a nickel wire 52 in series with a small coil 53 that is coupled to the inductance Ll of the oscillatory circuit. Lead 54 extends from the heater 5| to the coil L5 of a saturating core reactor that is coupled to the induct- The maximum 1o ance L2 of the oscillatory circuit of the external temperature control system, and the anode circuit is completed through lead 55 and a voltage drop resistor 55 to the +18 terminal of the plate current supply resistor II.- The rebalancing coil L3 of a saturating core reactor is connected between the anode end of the resistor 56 and ground through a variable sensitivity jadjusting resistor 51. The external temperature control system includes an instrument-controlled condenser C2, as in Fig. 5, for unbalancing the oscillatory circuit upon a departure of the external temperature from a selected normal value, an oscillator and amplifier network similar to that of Fig. 1 and as indicated by the block 0A, a relay [2 and motor M for adjusting the fuel supply valve l6,

and a rebalancing circuit comprising a coil L6 coupled to inductance L1 and in series with a variable iron-core inductance 58, 59, the core 59 being adjustable'as a function of the setting of the fuel valve I6.

The method of operationof the Fig. 6 dual control system is similar, in general, to that of the Fig. 5 circuit.- Variations in the temperature at the exterior of the heated receptacle result in small variations in the effective value of the condenser l, and thereby in correspondingly small adjustments of the fuel supply valve. Departures of the internal temperature from its desired value, as reflected in changes in the value of the condenser CI, alter the control point of the external control system in the following manner. Assuming that the internal temperature rises and thereby increases the capacity of the instrumentcontrolled condenser CI, the intensity of oscillation of tube 5 and the plate current of the amplifier tube It are decreased. This decrease in plate current flow results in an increase in the potential at the anode A of tube Ill, due to the lesser potential drop across the resistor 56, and the current flow through the rebalancing coil L3 is thereby increased. The immediate effect of this increased current flow to coil L3 is to increase the'tendency towards oscillation, thereby establishing an initial rebalance of the operating conditions in the internal temperature control sys tem. The rebalance results in a re-establishment of substantially the normal intensity of oscillation but at a higher value of the capacity Cl which represents a higher internal temperature.

The decrease in the plate current results in a. lowering of the temperature of the heating resistor 5|, and thereby in the resistance of the nickel wire 52 of the resetting circuit. This change takes place slowly and decreases the intensity of oscillation and establishes conditions for a rebalance only when the value of the capacity Cl decreases to a lower value corresponding to the original desired temperature within the heated receptacle.

In the external'temperature control. system, the

.eilect of the decreased plate currentflow in the tube 10 is to decrease the intensity of oscillation,

thereby producing the apparent efl'ect of an increase in the temperature at the exterior of the heated receptacle, whereby the external control system reacts to adjust the fuel supply valve l5 for a lowered heat input. The external control syster reaches a rebalance only when the temperature drops to a new value, corresponding to a reduction in the instrument-controlled capacity C2, to a new value that compensates for the unbalance created by the increased current flow through the coil L5.

For simplicity of illustration and description,

control basis, i. e. may be set at diflerent values during the progress of some heating operation or process. The program control may be eflectedby altering the current flow to a saturating core balancing reactor or by shifting the relatively stationary'vane of the miniature control con-' denser manually or by a clock-controlled motor and worm and gear system similar to the elements It, IQ of the Fig. control system. Furthermore, the initial unbalance of the control system may be obtained by one or a plurality of means other than an instrument-controlled capacity. inductance or coupling. The external temperature control system a: Fig. 6 is an example of a control in response to a plurality of factors, 1. e.

both the instrument-controlled capacity C! and the current flow through winding L5 affect the balance of the oscillatory circuit. The values of these factors may vary simultaneously, and in the same or in opposite sense so far as concerns the balance of the oscillatory circuit. The unbalancing effects of the changes in a plurality of control factors may be additive or they may neutralize or partially neutralize each other.

The wide latitude in the design or control of recording circuits embodying the invention is indicated by the foregoing descriptions and accompanying circuit diagrams, and it is to be understood that other variations that may occur to those familiar with this art fall within the spirit of my invention as set forth in the following claims.

I claim: I

1. In an electronic measuring or control apparatus responsive to an unbalance in the operating. conditions affecting a process or apparatus, the combination with an electronic tube, an input circuit network coupled to said tube and including means responsive to an unbalance of operating conditions to alter the current output of the tube, and an output circuit network coupled to said tube and including means operative by an altered current output to re-establish a bal-'- ance of the operating conditions, of time-delay conditions to a balance at the values existing prior to the unbalance, and means operative upon a departure of the magnitude of said current output from a preselected range of values to render said time-delay means inoperative to reset the operating conditions to a balance at the values existing prior to an unbalance.

2. In an electronic measuring or control apparatus responsive to an unbalance in the operating conditions ail'ecting a process or apparatus,

the combination with an electronic tube, an input circuit network coupled to said tube and including means responsive-to an unbalance of operating conditions to alter the current output of the tube, and an output circuit network coupled to said tube and including means operative by an altered current output to re-establish a balance of the operating conditions, of time-delay means responsive to an initial change in the current output to produce a further change of the current output in the same sense as the initial change, thereby to reset the operating conditions to a balance at the values existing prior to the 12 unbalance, and means operative upon a departure of the magnitude of the said current output from a preselected range of values to reverse the sense of the current output change produced by said time-delay means.

3. An electronic measuring or control apparatus responsive to variations in the magnitude of a. selected factor and of the type including an electronic oscillator tube, an oscillatory circuit coupled to said tube'and normally balanced to establish a preselected normal intensity of oscillation and thereby a preselected oscillatory current output from said tube, means responsive to the variation of the selected factor from a preselected value to disturb the normal balance of said oscillatory circuit and thereby alter the intensity of oscillation and the current output from said tube, and means responsive to an alteration in the tube output current to rebalance the oscillatory circuit to restore the intensity of oscillation to the preselected normal value, characterized by the fact that one of said means comprises a saturating core reactor for reflecting an impedance change into said input circuit network upon variation of the current in the direct current coil of the saturating core reactor.

4. An electronc measuring or control apparatus responsive to variations in the magnitude of a selected factor and of the type including an electronic oscillator tube, an oscillatory circuit coupled to said tube and normally balanced to establish a preselected normal intensity of oscillation and thereby a preselected oscillatory current output from said tube, means responsive to the variation of the selected factor from a preselected value to disturb the normal balance of said oscillatory circuit and thereby alter the intensity of oscillation and the current output from said tube, and means responsive to an alteration in the tube output current to rebalance the oscillatory circuit to restore the intensity of oscfllation to the preselected normal value, characterized by the fact that said rebalancing means comprises a saturating core reactor for reflecting an impedance change into said input circuit network upon variation of the current in the direct current coil of the saturating core reactor.

5. An electronic measuring or control apparatus as claimed in claim 4, wherein said apparatus includes a controlled device operable in opposite directions in accordance with the departure of the tube output current from the preselected value corresponding to a balanced condition of said oscillatory circuit, and said rebalancing means includes means operable by said controlled device for adjusting the current through said saturating core reactor. I

6. An electronic measuring or control appara-- tus as claimed in claim 4 wherein said rebalancing means includes a source of direct current and a multiple section network comprising the v tube and normally balanced to establish a preselected oscillatory circuit flow in the output section of said network, means responsive to variations in a selected control factor to disturb, the

normal balance and thereby alter the output current flow in the output section of the network,

characterized by the fact that said rebalancing means includes a saturating core reactor having a direct current core-saturating winding connected between points in the output section of said netwok across which the direct current potential drop varies with change in the oscillatory current flow in said output section network, the alternating current winding of said saturat-' ing core reactor being included in the input section of said network to affect the balance thereof.

8. In an electronic measuring or control apparatus, an electronic oscillator tube and associated normally balanced oscillatory circuit for determining the frequency and magnitude of the oscillatory current output of said tube, a con- 7 trolled device operable in response to departures of the current output of said tube from a preselected normal value, a saturating core reactor for reflecting an impedance change into said oscillatory circuit, and meansmovable by said controlled device to control the impedance reflected into said oscillatory circuit by said saturating core reactor, thereby to rebalance the oscillatory cir-- cuit upon an initial unbalance thereof that alters the current output of said tube, a

9. In an electronic measuringor control system responsive to variations in the magnitude of a selected control factor, an-electronictube, an

the input circuit network at a new control factor I value differing from said preselected desired value,

and time-delay means including a temperaturevariant impedance for resetting said input circuit network in balance at the preselected desiredvalue of said factor. i I 1 10. In an electronic measuring or control system, the invention as set forth in claim,9, in

'14 paratus, the combination with an electronic oscillator tube, an amplifier tube, workingout of said oscillator tube, a circuit network associated with said tubes and normally balanced to establish a preselected current output for said amplifier tube, said network including an oscillatory input circuit for said oscillator tube, means responsive to the departure of a selected control factor from a desired value to unbalance the network and thereby alter the current output of said amplifier tube, and means responsive to a variation of the amplifier tube current output to rebalance said circuit network at a new control factor value differing from said desired value, of time-delay means for resetting said circuit network in balance at saiddesired value of'the selected control factor. f I 1 13. In an electronic measuring or control apparatus, an electronic oscillator tube, an amplifier tube working out ofsaid oscillator tube, a circuit network associated with said tubes and normally balanced to establish a preselected current output for said amplifier tube, said network including an oscillatory input circuit'for said oscillator tube and means responsive to the departure of a selected control factor from adesired value to unbalance the network'and therebyialter the current output of said amplifier tube, and means responsive to a variation-of the amplifier tube current output to rebalance said circuit network at a, new control factor value differing from said desired value, said rebalancing means including an inductancecoupled to said oscillatory input circuit, a, variable impedance in circuit with said inductance, and meansnesponsive to a variation in the current output of said amplifler tube to alter the eflective ,magnitudeof said variable impedance I 1 g 14. In an, electronic measuring or control apparatus, the combinationwith --an electronic oscillator tube, an oscillatorycircuit coupled to said tube and normally balanced :to establish a predetermined normal current output from saidtube,

" means responsive to, a departure. of a, selected combination with means for rendering said timedelay means inoperativeto resetthe input cir- 'cuit network in balance at the preselected desired value of said factor.

l1. Inanelectronic measuring or control system responsive to variations in the magnitude of a selected control factor, the combination with an electronic tube, an input circuit network coupled to said tube and normally balanced at a preselected desired valuelof said control factor to develop a predetermined currentoutput from said tube, an output circuit network coupledto-said tube and including means responsive toa departure of the tube output currentfrom said predetermined value to re'balance the input circuit 7 network at a new control factor value differing from saidpreselected desired value, time-delay means for resetting said input circuit network in balance at the preselected desired value of said factor, and automatic means for reversing the sense of operation of, said time-delay resetting means, upon a, departurejof the magnitude of said control factor in a given sense from the normal control range that includes, said preselected desiredvalue, to shift the control range in the given sense from its normal control range "value.

12. In an electronic measuring or control apcontrol'jfactor; from apreselected desired value to unbalancesaid oscillator-y circuit andthereby alter the current output of said: tube;-and means responsiveto a variationinthe current output of said .tube to rebalance said'oscillatory circuit at the new control factor value differing from said preselected desiredvalue, thereby to' restore the current output of saidtube' to its preselected normal value, of time-delay means for resetting said oscillatory circuit'in .balance at the preselected desiredvalue of-said control factor;

15.,In .anelectronic measuring or control apparatus,- the:inventiondasrecited in 'claim l4 wherein said resetting means comprises atemperature-varient impedance coupled to said oscillatory circuit, a'heater resistance for determining the effectivevalueof said-impedance as a function;of current flow through said heater resistance, and means responsive to a departure of the current output ofjthe tube fromits nornial value to alter the current through said heater "resist p j .iii 111 I 16 man electronics-measuring or control apparatus, the invention as recited in, claim ,14 wherein said resetting means comprises a pair of temperature-variant impedances coupled to said oscillatory circuit and operative upon like variat o in m ni d qaff ct nlop sitec sens the current output of said tube, a heater resistance associated with each of said impedances to desame current output of the tube from its normal value i to alter in opposite sense the current flows to the respective heater resistances.

1'1. In an electronic measuring or control apparatus, the invention as recited in claim 14' wherein said resetting means comprises a pair of temperature-variant condensers coupled to said oscillatory circuit, an increase in the values of said condensers tending respectively, to increase and to decrease the oscillatory current output of said tube. a heater resistance for each condenser, and means responsive to a departure of the current output of said tube from its normal value to alter in opposite sense the currents supplied to the respective heater resistances.

18. In an electronic measuring or control apparatus, the invention as recited in claim 14 wherein said resetting means comprises a pair of temperature-variant impedances connected to said oscillatory circuit and operative upon like variations in magnitude to ail'ect in opposite sense the current output oi said tube, a heater resistance associated with each of said impedances to determine the effective magnitudes of said impedances, and means for altering in opposite sense the currents supplied to the respective heater resistances; said last means including a pair of cur-- rent-flow control elements, circuits including a polarity reversing switch connecting the respective current-flow control elements to said heater resistances, means responsive to limited magnitude departures of the current output of the tube from its normal value to adJust said current- 6 a current now in said output circuit, and means to rebalance the oscillatory circuit at a control factor value differing from said preselected value, thereby to restore the current flow in said output circuit to its preselected normal value; one of said means comprising a reactance of variant effective magnitude in said oscillatory circuit for atiecting the balance thereof, and means'including an adcontrol elements in opposite sense, and means responsive to larger magnitude departures of said tube current output from its normal value to paratus, the invention as recited in claim 14 wherein said oscillatory circuit comprises a pair of coupled coils; and said resetting means comprises a circuit including in series an inductance coupled to one of said coils and a temperaturevariant resistance, a heater resistance thermally coupled to said temperature-variant resistance, and means responsive to a departure of the current output-of said tube from its selected normal value to alter the current to said heater resistance.

20. In an electronic measuring ,or control apparatus, the invention as recited in claim 14 wherein said oscillatory circuit comprises a pair of coupled coils; and said resetting means comprises a pairof circuits each including in series an inductance coupled to a coil of said oscillatory circuit and a temperature-variant resistance, a heater resistance thermally coupled to each temperature-variant resistance, and means responsive to a departure of the current output of said tube from its normal value to alter in opposite sense the currents through the respective heater resistances. I

21. In an electronic measuring or control apparatus, an electronic oscillator tube, a circuit network including an oscillatory circuit conditioning said tube to operate as'an oscillator, and an output circuit for said tube, said oscillatory circuit being normally balanced to establish a predetermined normal current flow in said output circuit, means responsive to a departure of a selected control factor irom a preselected value to unbalance said oscillatory circuit to alter the magnitude of said reactance. I

22. In an electronic measuring or control apparatus, the combination of an electronic oscil-. lator .tube, an oscillatory circuit coupled to said tube and normally balanced to establish a prede-. termined normal current output from said tube, means responsive to a departure of a selected control factor from a preselected desired value to unbalance said oscillatory circuit and thereby alter the current output of said tube, and means to rebalance said oscillatory circuit at the control factor value diflering from said preselected desired value, thereby to restore the current output of said tube to its preselected normal value; said rebalancing means including an inductance coupled to said oscillatory circuit, a variable impedance in circuit with said inductance, and

means responsive to a departure of the current output of said tube from its normal value to alter the effective magnitude of said variable impedance. I

23. In an electronic measuring or control apparatus, the invention as set forth in claim 22,

wherein said last means comprises an adjustable resistance.

24. In an electronic measuring or control'apparatus, the invention as set forth in claim 22, wherein said last means comprises a metal-cored inductance, and means for adjusting the position of the core with respect to the associated inductance.

25. In an electronic measuring or control apparatus, the invention as set forth in claim 22, in combination with time-delay means responsive to an initial unbalance of said oscillatory circuit to eflect a further unbalance thereof in the same sense and of a magnitude of the order 0f the initial unbalance, thereby to reset the oscillatory circuit to a balance at the preselected desired value of the control factor.

26. In heating apparatus, an outer chamber and means for supplying heat energy thereto, an inner chamber for receiving material to be heated, a device adjustable to regulate the supply of heat energy to said outer chamber, and means for adjusting said device; said adjustingmeans comprising a control apparatus including an element responsive to the temperature within said outer ch-amber and'means to adjust said device to maintain the outer chamber temperature at a selected value, and a second control apparatus including an element responsive to the temperature within said inner chamber and means to adjust said first control apparatus to alter the selected control value of the temperature to be established within said outer chamber.

27. In heating apparatus, the invention as recited in claim 26, wherein said second control apparatus includes time-delayed resetting means to rebalance said second control apparatus at a preselected temperature value that is to be maintained within said inner chamber.

28. In heating apparatus, the invention asrecited in claim 26, wherein said second control apparatus comprises an electronic control apparatus including an electronic oscillator tube 17 and an oscillatory circuit coupled to said tube and normally balanced to establish a preselected normal oscillatory current output from said tube, means to unbalance said oscillatory circuit upon a departure of the inner chamber temperature irom its selected control value, thereby to alter the current output of said tube, means responsive to the altered current output to vary the selected control value of the outer chamber temperature, and means responsive to the altered current output to rebalance said oscillatory circuit to restore the current output to its preselected normal value at the then existing temperature within said inner chamber.

29. In heating apparatus, the invention as recited in claim 26, wherein said second control apparatus comprises an electronic control apparatus including an electronic oscillator tube and an oscillatory circuit coupled to said tube and normally balanced to establish a preselected normal oscillatory current output from said tube. means to unbalance said oscillatory circuit upon a departure of the inner chamber temperature from its selected control value, thereby to alter the current output 01 said tube, means responsive to the altered current output to vary the selected control value of the outer chamber temperature, means responsive to the altered current output to rebalance said oscillatory circuit to restore the current output to its preselected normal value at the then existing temperature within said inner chamber, and time-delay resetting means for restoring said oscillatory circuit to balance at the preselected control value of the inner chamber temperature.

30. In heating apparatus. an outer chamber and means for supplying heat energy thereto, an inner chamber for receiving material to be heated, a device adjustable to regulate the supply of heat energy to said outer chamber, and means for adjusting said device in accordance with temperature fluctuations within either or both of said chambers; said adjusting means comprising a primary and a secondary control apparatus each including an electronic oscillator tube and an oscillatory circuit coupled to the tube to determine the oscillatory current output thereof, means to unbalance the oscillatory circuits of the primary and secondary control apparatus upon departures from selected control values of the temperatures within said inner and said outer chamber respectively, thereby to alter the output currents of the respective tubes, means responsive to a departure from normal of the output current of either tube to rebalance the associated apparatus to restore the tube output current to its normal value, means responsive to an unbalance of the secondary control apparatus to ad-, just said device to alter the rate oi! supply of heat energy to said outer chamber, and means responsive to an unbalance of the primary control apparatus to unbalance the secondary. control apparatus, thereby to effect an adjustment of said device and a rebalance of the secondary control apparatus at a new selected control value.

31. In heating apparatus, an outer chamber and means for supplying heat energy thereto, an inner chamber for receiving material to be heated, a device adjustable to regulate the supply of. heat to said outer chamber, and means for adjusting said device to maintain the inner chamber temperature at substantially a constant selected control value; said adjusting means comprising a primary electronic control apparatus responsive to temperature within said inner chamber to vary the magnitude of the temperature to be maintained within said outer chamber, a secondary electronic control apparatus responsive to temperature within said outer chamber to adjust said device to maintainjhe outer chamber temperature at the magnitude determined by said primary control apparatus.

32. In heating apparatus, the invention as set forth in claim 31, wherein said secondary electronic control apparatus includes an electronic oscillator tube, an oscillatory circuit coupled to said tube and normally balanced to establish the current output from said tube at a selected normal value, means responsive to a change in said current output to adjust said device, means responsive to a departure of the inner chamber temperature from the then existing control magnitude to unbalance said oscillatory circuit, thereby to alter the current output of said tube, means controlled by said primaryelectmnic control apparatus to unbalance said omillatory circuit, and means responsive to a change in the output current of said tube to rebalance the oscillatory circuit to restore the current output 'at its selected normal value.

33. In heating apparatus. the invention as recited in claim 3i wherein said second electronic control apparatus includes a temperature-measuring system having a pointer carrying a vane and a relatively stationary cooperating element,

the position of said vane with respect to said element controlling the operation of said secondary electronic control apparatus; and said primary electronic control apparatus includes means for displacing said relatively stationary element uponv a departure of the inner chamber temperature from a. selected value.

34. An electronic measuring or control apparatus for automatically maintaining desired conditions during the operation of a major apparatus, said measuring and control apparatus comprising an electronic tube, an oscillatory circuit coupled to said tube and normally balanced to establish a preselected oscillatory current output from said tube, a controlled apparatus selectively energized in accordance with departures of said current output from its preselected value corresponding to a balance of said oscillatory circuit, a plurality of means responsive to difierent control factors to unbalance said oscillatory circuit upon the departure of any coniaol factor magnitude from its selected value, and means responsive to a change in the output current to rebelance said oscillatory circuit to restore said output current to its preselected value.

35. An electronic measuring or control apparatus for automatically maintaining desired conditions during the operation of a major apparatus, said measuring and control apparatus comprising an electronic tube, an oscillatory circuit coupled to said tube and normally balanced to establish a preselected oscillatory current output from said tube, a controlled apparatus selectively energized in accordance with departures oi said current output from its preselected value corresponding to a balance of said oscillatory circuit, means responsive to changes in the value of V a control factor to unbalance said oscillatory circuit upon the departure of the control, factor magnitude from a selected value, additional means coupled to said oscillatory circuit for unbalancing the same thereby to condition said aposcillatory circuit to restore said output'eurrlit toits preselected value.

36. an electronic measuring apparatus for automatically desired conditions during the operation oi a'maior IP90.-

' I ratus, said measuring and control apparatus comprising an electronic tube, an oscillatory cir- .Q cult coupled to tube and normally balanced to establish a preselected'o'sclllatory out- I put from said tube, a controlled apparatus selectively energized in accordance with departures I of said'current output from its'preselected value corresponding to a balance of said oscillatory clrcult, a' measuring instrument having a moving system for displacing a p'ointerin' withfiuctuationsin the .magnitudeof a control factor, a vane on said pointer and movable thereby with respect to a relatively fixed element, said vane and cooperating; element constituting means for unbalancing said oscillatory circuit 5 upon a departure of the control factor magnitude from a preselected value, additional means oper-- I saieo ductances', and variable impedance is noncapacitive and variable inresponse to changes in the magnitude oi said variable control iactor.

' 40. Anelectronic' measuring or control apparatus of the type including an electronic tubehaving a resonant circuit network conditioning said ,tube to operate as-an oscillator, an output cirable automatically in accordance with the desired conditions to be maintained to unbalance said oscillatory circuit, and means responsive to a change in the tube output current to rebalance the oscillatory circuit to restore the tube output current to its preselected value.

37. An electronic measuring and control apparatus for automatically maintaining desired con- ,ditions'during the operation of a major apparatus, said measuring and control. apparatus cuit network, a device in the output circuit network responsive to variation in the tube output current, and means responsive to at least one variable factor for controlling the tube'output current; characterized by the fact that said means "includesa circuit coupled to one of said networks;

said circuit comprising,.in series, a temperaturevariant resistance and a coil coupled to an inductance in one of said networks, a heater resistance in heat-transfer relation to said resistance, and circuit means for establishing through said heater resistance a current that varies in magnitude with said factor.

41. An electronic measuring or' control apparatus as defined in claim 40, wherein said "first means includes a pair of circuits coupled to one of said networks; each circuit including a temperature-variant resistance in series with a coil coupled to an inductance in the network, a heater resistance in heat-transfer relation to each re4 sistance of the respective circuits, a current source for establishing currents through said heater resistances, and said circuit means adusts in opposite sense the currents through said heater resistances, and said circuit means adcomprislng an electronic tube, an oscillatory circuit coupled to said tube and normally balanced to establish a preselected oscillatory current output from said tube, a controlled apparatus selectively' energized in accordance with departures of, aid current output from its preselected value corresponding to a balance of said oscillatory cir- V 'cuit, a measuring instrument having a moving system for displacing a pointer in accordance with fluctuations in the magnitude of a control factor, a vane on said pointer and movable there by with respect to a relatively fixed element, said vane and cooperating element constituting means for unbalancing said oscillatory circuit upona departure of the control factor magnitude from f a preselected value, means operable automaticalrent is independent of fluctuations in the voltage or said current source.

42. In an electronic measuring or control circuit responsive to variations in the magnitude of. a selected control factor, the combination with an'electronic tube, an oscillatory circuit conditioning said tube for oscillation and normally balanced at a preselected control factor value to develop a predetermined oscillatory current output from said tube, said oscillatory circuit including coupled 'inductances, and an output circuit network for said tube including a device responsive to changes in the magnitude of said oscillatory output current, of variable impedance circuit means coupled to an inductance of said ly in accordance with the desired conditions to be I maintained to displace saidelement with respect to said vane,- thereby to unbalance said oscillatory circuit, and means responsive to a change in the tube output current to rebalance the oscillatory circuit to restore the tube output current to its preselected value. I

38. In anelectronic tube circuit, a tube, In oscillatory circuit coupled to said tube, an output circuit coupled to said tube, a coil coupled to said oscillatory circuit, a temperature-variant resistance in circuit with said coil. and a heater resistor in heat-transfer relation to said temperature-variant resistance.

' 39. An electronic measuring or control apparatus of the type including an electronic tube having a resonant circuit networkincludlng a pair,

or coupled inductances and associated capacitive impedancejconditioning said tube to operate as an oscillator, an output circuit network, a device in the output circuit network responsive to variation in the tube output current, and a circuit including a variable impedance controlled by .a

variable factor for affecting the balance condition of the networks and thereby the tube output current; characterized by the fact that said circuit is inductively coupled to one of said inoscillatory circuit for aiiecting the balance of said oscillatory circuit, thereby to change the magnitude of the oscillatory current output; said variable impedance circuit means including a variable non-capacitive impedance element and a coil comprising a few turns of wire inductively coupling said variable impedance circuit means to an inductance of the oscillatory circuit.

43. In an electronic measuring or control circuit, the invention as recited in claim 42, wherein said variable impedance element comprises a temperature-variant resistor, and means controlled by sald device for regulating the temperature of said resistorin accordance with the magnitude of the oscillatory current output, whereby the effective resistance of said resistor varies with the oscillatory current output to afiect the balance condition of said oscillatory circuit.

44. An electronic measuring or control apparatus of the type including an electronic tube having a resonant circuit network conditioning said electronic tube to operate as an oscillator and an output circuit network, a device in the rent; characterized by the fact that said circuit is inductively coupled to said resonant circuit network and includes a variable magnitude noncapacitive impedance comprising a coil and a metal member movable with respect to the coil to vary the inductive impedance.

45. An electronic measuring or control apparatus of the type including an electronic tube having a resonant circuit network including a pair of coupled inductances and associated capacitive reactance conditioning said electronic tube to operate as an oscillator, one of said inductances having a grounded terminal, an output circuit network; a device in the output circuit network responsive to variations in the tube output current, and a circuit for affecting the balance condition of said resonant circuit network and thereby the tube output current; characterized by the fact that said circuit includes a variable magnitude non-capacitive impedance and is inductively coupled to said grounded inductanceat the end thereof adjacent the grounded terminal.

46. An electronic measuring or control apparatus as recited in claim 45, wherein said circuit REFERENCES cn-En The following references are of'record in th file of this patent;

UNITED STATES PATENTS Name Edwards et al Number M 1,951,276 r Mar. 13, 1934 

